1. Field of the Invention
The present invention relates to a stationary generator system which is equipped with a fuel cell and which fuel, such as natural gas or the like, is reformed with the aid of water vapor to generate fuel gas containing hydrogen gas. This fuel gas is electrochemically reacted with an oxide gas, such as oxygen, in air to generate electric power. The present invention also relates to a method for operating such a generator system.
2. Description of the Related Art
Cooling water is traditionally used in a fuel cell generator system to regulate the temperature in the fuel cell to increase the efficiency of electric power generation in the fuel cell. Cooling water is normally water that has been processed such as by desalinization.
FIG. 4 schematically illustrates a typical fuel cell generator system which includes a fuel cell 1, a water recovery system 2 for recovering water vapor as a condensate from exhaust gas discharged from the fuel cell 1, a water process system 3 for processing the water (raw water) recovered by the water recovery system 2 to supply the processed water as a cooling water to the fuel cell 1, a waste heat recovering heat exchanger 4 for recovering waste heat from fuel cell 1 to heat the water and a hot water storage vessel 5 for storing the hot water from the heat exchanger 4.
The water recovery system 2 is equipped with a condensate recovering heat exchanger 17 for cooling water vapor in the exhaust gas from the fuel cell 1 to generate a condensate, and s equipped with a recovered water storage vessel 18 for storing the recovered water (raw water to be processed as cooling water) obtained by condensation in the heat exchanger 17.
The water process system 3 is equipped with a water processing apparatus 6, such as a reverse osmosis separator, for removing impurities in the recovered water (the raw water to be processed as cooling water), a discharge line 7xe2x80x2 for discharging from of the system, water in which impurities are concentrated by the water processing apparatus 6, and a fluid feed pump P1.
Hot water storage vessel 5 is designed such that the hot water in the vessel can be supplied to an external heat installation (not shown).
In this fuel cell generator system, fuel such as natural gas is reformed in the fuel cell 1 with water vapor to generate fuel gas containing hydrogen gas. This fuel gas is electrochemically reacted with an oxidizable gas such as oxygen in air to generate electric power. At the same time, water vapor in the exhaust gas is cooled to generate a condensate in the condensate recovery heat exchanger 17, and then, the recovered condensate is stored in recovered water storage vessel 18.
Impurities, such as carbonic acid ions, metal ions, and the like, resulting either from the exhaust gas discharged from the fuel cell 1 or from supply water, may be found in the raw water stored in the recovered water storage vessel 18. Raw water is fed as cooling water to the fuel cell 1 after complete removal of the impurities by the water processing apparatus 6.
In the water processing apparatus 6, the water in which the removed impurities are concentrated is discharged from the system via the discharge line 7xe2x80x2 (e.g., to a sewer or the like).
When the amount of water in the recovered water storage vessel 18 falls below a predetermined level when it is used as cooling water, supply water such as tap water is fed to the recovered water storage vessel 18 via a supply water feed line 51.
When the amount of water in the hot water storage vessel 5 falls below a predetermined level when the hot water is supplied to the external heat usage equipment (not shown), supply water such as tap water is fed to hot water storage vessel 5 via a hot water feed line 52.
However, because concentrated water (which contains concentrated impurities) is discharged from the system from this water processing apparatus 6, the cost of processing the exhaust water in the system (for instance, the fee for tap water to be used) increases.
Accordingly, it is an object of the present invention to provide a fuel cell generator system which is capable of reducing the processing cost of exhaust water discharged from the system.
It is another object of the present invention to provide a method for effectively operating such a fuel cell generator system.
The first object of the present invention is achieved with a fuel cell generator system comprising: a fuel cell; a water process system for processing raw water to produce cooling water and for supplying the cooling water to the fuel cell; means for heating the water with heat generated in the fuel cell; and a hot water storage vessel for storing the hot water from the heating means, wherein the water process system comprises: a water processing apparatus for separating the raw water into cooling water with impurities removed and concentrated water with the impurities; and a concentrated water feed line for feeding the concentrated water to the hot water storage vessel.
In an aspect of the fuel cell generator system according to the invention, the water processing apparatus is equipped with a plurality of water processing units and one or more lines for collecting the concentrated water from water processing units other than the first water processing unit.
In another aspect of the fuel cell generator system according to invention, the water processing apparatus includes a reverse osmosis separator as a first water processing unit positioned at a first stage and an electric deionizer as a second water processing unit.
The second object of the present invention is achieved by operating a fuel cell generator system comprising: a fuel cell; a water process system for processing raw water to produce cooling water and for supplying the cooling water to the fuel cell; means for heating the water with the heat generated in the fuel cell; and a hot water storage vessel for storing the hot water from the heating means, wherein concentrated water in which impurities removed from the raw water in the water process system are concentrated is fed to the hot water storage vessel.
In the fuel cell generator system according to the invention, the water process system may be equipped with a water processing apparatus for removing impurities from the raw water used as the cooling water and may be equipped with a concentrated water feed line for feeding the concentrated water to the hot water storage vessel. The impurities are concentrated in the concentrated water by the water processing apparatus, so that the concentrated water discharged from the water processing apparatus can be supplied as supply water to the hot water storage vessel.
Consequently, the amount of the supply water, such as tap water, to be supplied to the hot water storage vessel can be reduced, which will lower the cost of supply water. Additionally, the amount of water to be discharged outside of the system can be decreased, which will lower the cost of processing waste water.
When the water processing apparatus in the fuel cell generator system of this embodiment includes a plurality of water processing units, the amount of water discharged from the water process system will not increase of the load to the water process system if the lines for collecting concentrated water from the water processing unit are not located at the first stage. This will increase efficiency of water and will reduce the cost of supplying water.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.